are greatly influenced by cultural preferences; therefore, broad generalizations are difficult. In a study on the effect of water temperature on voluntary drinking, dehydrated men drank the highest amounts when the water temperature was 15°C (59°F). Higher and lower temperatures resulted in a smaller drinking volume, even though the cooler drinks were rated more “pleasurable” (Boulze et al., 1983). In another study, water at 15°C (59°F) was consumed at greater volumes than water at 40°C (104°F) (Szlyk et al., 1989). When children were exposed to 3 hours of intermittent exercise at 35°C (95°F) and 45 to 50 percent relative humidity, their ad libitum consumption of flavored water was 45 percent greater than with unflavored water (Figure 4-13) (Wilk and Bar-Or, 1996). Likewise, adults who performed desert-simulated walks at 40°C (104°F) drank approximately 50 percent more flavored water than unflavored water (Hubbard et al., 1984).

The sweetness of a drink is a major factor in its palatability, but people differ in their preferred flavor. Flavor preference depends on various factors, including ethnic and cultural backgrounds. For example, in one study with Canadian children, most preferred grape to orange or apple flavors and drank more when presented with a

FIGURE 4-13 Cumulative voluntary drink intake of unflavored water (open circles), flavored water (black circles), and flavored sodium chloride (18 mmol/L) plus carbohydrate (6 percent) solution (triangles). Twelve 9- to 12-year-old boys cycled intermittently (black bars) at 35°C, 45 to 50% relative humidity. Reprinted with permission, from Wilk and Bar-Or (1996). Copyright 1996 by the American Physiological Society.